John Tyler (1790-1862), the tenth President of the United States, left office in 1845. Though quite old, he fathered a son in 1853. That son himself fathered two sons at an advanced age in 1924 and 1928. Those two men, the grandsons of President Tyler, are still alive:

That means just three generations of the Tyler family are spread out over more than 200 years. President Tyler was also a prolific father, having 15 children (8 boys and 7 girls) with two wives.

He even allegedly fathered a child, John Dunjee, with one of his slaves.

Some context on Tyler's progeny: Jane Garfield (granddaughter of James Garfield) is 99, making her the oldest living grandchild of a former president, even though Garfield took office 40 years after Tyler.

Former Ambassador John Eisenhower is the oldest living presidential child, turning 89 this past August.